The present invention generally relates to a forced-draft unit for use in conjunction with typical wood heaters or wood stoves in order to increase the combustion efficiency of the wood fuel.
In the prior art, typical wood heaters or wood stoves provided for a fresh air inlet at the bottom portion of one side of the combustion chamber and a flue outlet at the top portion of an opposite side of the combustion chamber. With this arrangement, the fresh air inlet provided air to the combustion chamber which consequently began to rise by virtue of the negative pressure region created by the flue outlet at the top portion of the opposite side of the combustion chamber. As a result, most of the incoming oxygen was not utilized in the combustion process, rather, immediately exited through the flue outlet providing a cooling effect to the wood stove. Further prior art devices attempted to correct this deficiency by providing a secondary combustion whereby the fresh air inlet would recirculate in the combustion chamber prior to exiting the flue outlet. However, by virtue of the locations of the fresh air inlet versus the exhaust gas outlet openings, much of the incoming oxygen remained unutilized with respect to the combustion process when being forced through the exhaust gas outlet and into the atmosphere. Even though some degree of secondary combustion was taking place, excess air within the exhaust gases still remained unutilized and an excessive quantity of unburned combustibles also remained thereby minimizing the total combustion efficiency, and in particular the efficiency of the secondary combustion process.
The present invention attempts to maximize and further improve the combustion efficiency relative to the above prior art devices, and in particular to improve the efficiency of the secondary combustion process by locating the fresh air inlet immediately adjacent to the flue or exhaust gas outlet opening, and further providing a means for generating a supply of forced draft air through the fresh air inlet so that a substantial quantity of the exhaust gases and unburned combustibles which are attempting to exit through the flue outlet are forced to recirculate back through the combustion chamber because of the high velocity of incoming forced draft air from the air inlet. This structural arrangement creates a secondary combustion, but also increases the efficiency of the secondary combustion by forcing the exhaust gases and unburned combustibles to recirculate and to again recirculate thereby utilizing to a maximum extent the excess air and unburned combustibles remaining in the exhaust gases prior to its eventual exiting through the flue outlet opening and into the atmosphere.
This improved secondary and primary combustion is accomplished by utilizing a blower which is attached to a plenum which is further attached to a panel on which the flue arrangement is mounted. The internal flue arrangement mounted on the interior of the wood stove communicates with the outer atmosphere thereby providing a means for the exiting of the exhaust gases after combustion. The air from the blower enters a set of air inlet openings and is further conducted through a set of ducts and exits through a set of air nozzle slits, is circulated through the combustion chamber creating exhaust gases having a specific quantity of excess air and unburned combustibles. The exhaust gases attempt to exit through the flue outlet opening which is located directly adjacent to the air nozzle slits but is forced to recirculate back into the combustion chamber by virtue of the high velocity incoming air entering the combustion chamber through the air nozzle slits. As a result, combustion efficiency is improved by virtue of the minimization of the excess air and unburned combustibles in the exhaust gases. Since the excess air has a tendency to cool the stove, by minimizing the excess air in the combustion process, a cooling effect of the stove is prevented, and additional heat is created thereby improving the combustion efficiency of the fuel in the stove.
Accordingly, one object of the present invention is to provide an attachment to a typical wood burning stove which will improve the combustion efficiency of the fuel thereby maximizing the heat generation capacity of the stove itself
Another object of the present invention is to provide a secondary combustion process as well as a primary combustion process in a singular combustion chamber of the fuel burning stove.
Another object of the present invention is to increase the combustion efficiency of the total combustion by recirculating the exhaust gases created during the combustion process thereby minimizing excess air and unburned combustibles present within the discharged products of combustion.
Another object of the present invention is to carefully choose the size of the forced draft air components to match the size of the combustion chamber thereby improving upon the primary and secondary combustion efficiency of the wood burning stove.
Still another object of the present invention is to eliminate smoke back when the front door of the wood burning stove is opened.
Another object of the present invention is to improve overall heat extraction or heat transfer by means of the inherently high internal turbulence of velocity of incoming forced air provided by the forced draft unit.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific example, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.